Cracking of hydrocarbons and treatment of residues



June 23, 1931. i E. w. :soM 1,811,272

CRACKING 0F HYDROCARBONS AND TREATMENT OF RESIDUES Filed June 30, 1924 2Sheets-Sheet l Condenser Receiver Reflux Tower Pressure 511' H CafingFurnare Edward 'W. 150m ATTORNEYS June 23, 1931.

E. W. ISOM CRACKING OF HYDROCARBONS AND TREATMENT OF RESIDUES Filed June30, 1924 2 Sheets-Sheet 2 INVENTOR Edward W. 160m ATTORNEYS PatentedJune 23, 1931 UNEED STATES ATEN OFFICE EDWARD W. ISOM, OF WINNETKA,ILLINOIS, ASSIGNOR T0 SINCLAIR REFINING COM- PANY, OF CHICAGO, ILLINOIS,A CORPORATION OF MAINE CRACKING OF HYDROCARBONS AND TREATMENT OFRESIDUES Application filed June 30,

This invention relates to improvements in the cracking of heavierhydrocarbon oils for the production of lighter hydrocarbon oilstherefrom. More particularly, it relates to 5, improvements in theoperation of pressure stills for the cracking of heavier hydrocarbonoils, such as gas oil, etc., for the production of gasoline or so-calledpressure distillate therefrom.

1o The invention includes improvements in the method of pressuredistillation, and more particularly it includes improvements in a cyclicprocess in which tar is drawn off from the pressure still and speciallytreated to separate the tarry constituents from the oil accompanyingthem, and in which the separated oil is returned to the pressure stillfor further cracking.

v The invention also includes an improved methodof treating the tar orresidue from pressure stills for the separation of tarry andcarbonaceous matter therefrom and for the separation and recovery of theoil accompanying such constituents so as to make it available forfurther use either in the pressure still or for other purposes.

When heavier. hydrocarbon oils, such as gas oil, etc., are subjected tocracking at high temperatures and pressures in pressure stills,

the cracking operation is accompanied by the formation of tarry orcarbonaceous constituents which accumulate in the oil of the charge. Asthese tarry or carbonaceous constituents increase in amount, there anincreased tendency for these constituents to separate out on the heatedwalls or heated surfaces of the still. In order to reduce this danger,tar is sometimes drawn off from the pressure still during the progressof the cracking operation and additional fresh charging stock or oil issupplied to the still to prevent the content of tar or carbonaceousmatter from increasing to an objectionable degree. 'yyhere such tar iswithdrawn during the progress of the cracking operation, the amount ofthe tar withdrawn often amounts to a large proportiolfof the total oilcharged into the cracking still; and relatively large amounts of suchtar are produced n so the aggregate, since, by withdrawmg tar in 1924.Serial No. 723,081.

this way, the cracking operation can be pro longed for a considerablylonger period of time than would be feasible if all of the tar werepermitted to remain and accumulate in the pressure still itself.

The present invention relates particularly to the treatment of this tar,withdrawn from the pressure still during the progress of the crackingoperation, and withdrawn from the still at the end of the crackingoperation; and

the present invention provides an improved process whereby the tar sowithdrawn may be directly treated for the separation of the tarry orcarbonaceous materials from the accompanying oil, and the oil madeavailable for return to the cracking still freed from all or the greaterpart of these tarry or carbonaceous constituents.

According to the present invention, the socalled tar withdrawn from thepressure still is admixed with finely divided fullers earth or similarmaterial, and the fullers earth or similar material is brought intointimate contact with all parts of the tarry oil. When the fullers earthhas been intimately distributed throughout the tarry oil, the fullersearth and tarry or carbonaceous constituents are separated from the oilfor example, b settling, leaving oil free or relatively free rom tarryand carbonaceous constituents. This oil can then be returned to thepressure still for further treatment during the progress of the crackingoperation.

Fullers earth appears to have an afiinity for the tarry constituentsproduced during the cracking of heavier petroleum oil. en it isintimately admixed with and distributed throughout the pressure stilltar, it tends to accumulate and adhere to the carbonaceous and tarryconstituents. Apparently the finely divided particles of fullers earthact as nuclei about which the tarry or carbonaceous particles collect sothat the fullers earth has a clarifying action with reference to theseconstituents, leaving the body of 011, from which the fullers earth andadmixed and attached tarry constituents have settled, relativelyfreefrom such constituents.

The amount of fullers earth used in treating the pressure still tar willvary somewhat example, the pressure still tar may urated orsupersaturated with such tarry constituents will ordinarily require morefinely-divided fullers earth than pressure still tar which is drawn offbefore the tarry constituents become saturated in the oil in which theyare formed by the cracking operation. In general, the amount of fullersearth should be suflicient so that after the fullers earth is intimatelydistributed throughout the oil and the oil is permitted to. settle orotherwise subjected to separation, the fullers earth will remove with itall or the greater part of the tarry constituents, leaving the oilsufliciently clarified for re1ntroduction into the pressure still or foruse for other purposes.

7 The treatment of the pressure still tar With the finely dividedfullers earthlcan be carried out in various types of apparatus andaccording to various methods of procedure. For

be collected in a storage tank and the finely divided -fulle-rs earthadded thereto and intimately admixed therewith, and the fullers earthand tar may then be permitted to settle, the fullers earth dragging thetar to the bottom of the tank and leaving the relatively tarfree oil sothat it can be drawn off after the settling has taken place. Such asettling tank'may be provided with agitators 0r stirrers, for stirringthe fullers earth into the oil and insuring intimate distribution of thefullers earth throughout the tarry oil.

Instead of treating a batch of pressure still tarin this way, thetreatment can be made more or less continuous, for example, by addingthe fullers earth in regulated amounts continuously or intermittently toregulated amounts of the pressure still tar and causing thoroughagitation of the earth and tar in a continuous manner, for example, bypassing the tar with admixed fullers earth through an agitatingapparatus where the fullers earth is intimately distributed throughoutthe pressure still tar. After this intimate distribution has takenplace, the tar and admixed fullers earth can then be run into settlingtanks and the fullers earth and tar permitted to settle so that. the oilfromwhich the tar has been more or less completely settled can then bedrawn ofi' andreturned to the pressure still.

Inasmuch as the pressure still tar is drawn off at a high temperature,and is more thinly fluid at such high temperatures than after cooling,the admlxture of the tar with fullers earth andthe treating operationcan be carried out with the hot .tar, and the fullers earth and tarseparated therefrom while the remaining oil is still hot; and theclarified 011 can be returned to the pressure still and its heat to agreater or less extent conserved and utilized both in the fullers earthtreatment and in avoiding the necessity for re hteillting theoil uponits return to the pressure s 1 Or the pressure still tar may be cooledafter it is withdrawn from the pressure still todecrease the solubilityof the tarry and pitchy constituents in the accompanying oil and toassist in the separation of the tarry and carbonaceous materials bydecreasing their solubility in the oil. The tar withdrawn from thepressure still maybe cooled before it is subjected to treatment with thefullers earth; or the admixture of the tar with the fullers earth canbecarried out with the hot tar and the admixed tar and fullers earthcooled before or during separation of the fullers earth and tarryconstituents retained by the fulle'rs earth. I A lighter oil may beadded to the tar withdrawn from the pressure still to assist in theseparation of tarry and carbonaceous constituents by the fullers earthtreatment. For example, a gas oil or kerosene character fraction maybeadded to the pressure still tar before it is admixed with the fullersearth.

The lighter oil added to the pressure still tar may be, for example,pressure distillate bottoms from the fractionation of crude pressuredistillate or a suitable fraction derived from crude pe roleum.- Wherethe treated oil from which tarry and carbonaceous constituents have beenseparated is returned to the pressure still, the added oil isadvantageously of a character suitable as a part of the charging stockgoing to the pressure still. Where a lighter oil is mixed with thewithdrawn tar to assist in the separation of tarry constituents, a partof the fresh charging stock to the pressure still may be added to thetar before treatment with the fullers earth and introduced into" thepressure still with the treated and clarified oil.

Before the treatment with fullers earth,

a part of the lighter oily constituents withdrawn with the tar from thepressure still may be separated by vaporization and condensed andreturned to the pressure still or otherwise disposed of without goingthrough the treatment with fullers earth. The hot tar withdrawn from thepressure still under pressure may be subjected to reduced pressure whilehot and a part of the lighter oily constituents accompanying the tarvaporized by the reduction in pressure and the tar cooled by thevaporization. The unvaporized tar may then be admixed with the fullersearth and the earth and admixed and attached tarry and carbonaceousmaterials separated from the remaining-unvaporized oil. The treated andclarified oil can be returned to-the presr sure still or used for otherpurposes.

The invention is of more 'or less general application to the treatmentof pressure still tar from various cracking operations in which such taris formed. It is particularly advantageous however for the treatment ofpressure still tar such as is drawn oil from cracking stills during theprogress of the cracking operation and in which the tarry constituentsdo not greatly exceed in amount that which will saturate the oil inwhich they are contained. The amount of such constituents may even beless than that which will cause saturation" of the oil carrying them,although the amount may be considerably in excess of the saturationpoint, particularly toward the end of the cracking operation. Theinvention is thus of particular value in connection with so-calledsemi-continuous operation of pressure still in which, during the latterpart of a pressure still run, tar is drawn off more or less continuouslyand in relatlvely large amount in the aggregate, and in which the tarryconstituents are admixed with and car ried' by a relatively large amountof oil suitable .for charging stock in the cracking process from whichthe oil and tar are withdrawn.

Thei separationof the fullers earth and tar from the treated andclarified oil can be effected in various ways. Instead of per- -mittingthe fullers earth and tar to settle from the supernatant oil, theseparation can be efiected by centrifugal means or by filtration, andthis separation can be carried out either upon successive batches of theoil, or in a more or less continuous manner.

- The improved oil product of the invention from which the tar has beenseparated by the fullers earth treatment is of the same, orsubstantially the same, composition as the oil in the pressure stillfrom which the tar is withdrawn, except that it has been separated fromall or the greater part of its tarry constituents. The fullers earthtreatment, moreover, has a purifying and clarifying eflect upon the oil,so that after the separation of the fullers earth and tar, the clarifiedoil is particularly advantageous for return to the cracking still foradmixture with the oil undergoing cracking therein. The improved oilproduct is of low viscosity, due to the cracking treatment to which ithas been subjected, and is of advantage for use as a fuel oil where aclean oil is necessary or desirable. The treated and clarified oil issubstantially free from constituents tending to deposit in feedconnections or in burners. v

The present invention accordingly provides an improved cyclic process inwhich tar withdrawn from a pressure still is subjected to a refiningoperation with fullers earth, to separate all or the greater part of thetar from its accompanying oil, and in which the separated oil isreturned to the pressure still to undergo further cracking therein.

This cyclic process can advantageously be carried out in conjunctionwith pressure stills such as are now operated according to the the tarto be recovered in a form well adapted for return to the pressure stillfor use in the further carrying out of the same pressure distillationoperation.

Instead, however, of returning the clarified oil to the same pressurestill during the same runfrom which the oil is withdrawn, it can bestored until needed and used as fresh charging stock at the beginning ofthe operation of a pressure still, or it can be introduced into someother pressure still, either as a part of the charge, or continuously,or at successive times during the progress of the cracking operation.

The fullers earth treatment of the present invention does not introduceinto the oil any objectionable or undesirable constituents; rather ittends to free the oil from undesirable constituents, particularlysulfur-containing constituents which the oil and particularly the tarcontained in the oil may contain; and it does not subject the oil tocracking decomposition.

Considered as a cyclic process, the present invention accordinglyinvolves first carrying out the pressure distillation with theproduction of tar or tarry constituents in amounts sufficient to make itdesirable to withdraw tar during the cracking operation; treating thewithdrawn tar with fullers earth to separate the tarry constituents fromthe oil in which they are contained; and returning the oil from whichthe tarry constituents are thus separated, to the cracking still.

When this treatment is carried out upon hot tar, the oil returned to thestill may still retain a considerable amount of the heat con tained inthe tar as withdrawn; and the fullers earth treating operation ispromoted by the fluidity of the hot tar and the increased facility withwhich the earth can be admixed therewith and the admixed earth and tarsettled therefrom.

The tar or tarry residue produced by socalled digestion processes, orthe tar or tarry residue remaining after the vaporization of part of theoil by the self-contained heat of the tar or synthetic crude or othercracked product, can be similarly treated according to the fullers earthtreatment of the present invention for the separation of the rtarryconstituents from the oil in which they are contained; and the clarifiedoil can be returned if desired to the cracking process or admixed withfresh charging stock for the cracking process, or used for otherpurposes.

Instead of using divided fullers earth for treating the pressure stilltar or similar tar, other similar adsorbent materials having a similarclarifying eflect may be used. Certain other clays or acid-treated clayscan be used in a similar manner, as can also materials like silica-gel,although fullers earth is well adapted for use in the process and itsavailability and low cost make it particularly advantageous.

The invention will. be further described and illustrated in connectionwith the cracking of oils in a pressurestill'of the general constructionillustrated in United States Letters Patent No. 1,285,200 granted to theSin-. clair Refining Company, November 19, 1918, upon'the application ofEdward W. Isom.

The accompanying drawings show in a somewhat conventional anddiagrammatic manner in Fig. 1a pressure still ofthe gen eralconstruction illustrated in said patent, together with a diagrammaticrepresentation of apparatus in Fig. 1A appropriate for use in thecarrying out of the fullers earth treatment and. in the carrying out ofthe cyclic process of the invention. The drawings are not intended torepresent to scale the apparatus diagrammatically illustrated.

The pressure still illustrated in the drawings is made up of the bulksupply tank 1 located away from the heating furnace 2, the Verticalheating tubes 3 arranged in the heating flue of the furnace, andcirculating'pipes 4, 5 and 6 connecting the lower and upper ends of thevertical tubes with the bulk supply tank and a circulating pump 7 forcirculating the oil from the bulk supply tank through the vertical tubesand back to the bulk supply tank. Arranged above the bulk supply tank isthe reflux tower 8 having a series of bafiles therein and beingconnected with the vapor dome of the bulk supply tank through the vaporline 9. An overflow reflux line 10 leads back to the pipe line leadingfrom the bulk supply tank to the circulating pump. The vapors from thetop of the reflux tower escape through the vapor line 11 to thecondenser 12, where the vapors are subjectedto condensation. Thecondenser discharges into the receiver 13, from which the uncondensedvapors and gases are withdrawn through connection .14 and the condensatethrough connection 15. A feed line 16 is provided for feeding freshcharging stock to the reflux tower 8. An additional feed line 17 isprovided for feeding fresh oil to the circulating stream of oil throughthe pump 7. A tar draw-01f 18 is provided adapted for use during theoperation of the pressure still. A pumping out line for discharging thestill is shown at 19. For pumping out the still, the valve 20 in theline 21 is closed and the valve 22 in the pumplng out line 1s opened.

The pressure may be regulated and reduced by means of a. regulatingvalve 23 between the reflux tower and the condenser, or by regulation ofvalves in the connections 14 and 15 beyond the receiver.

The tar draw-off 18 is arranged to discharge into a receiving tank 24.The rate of withdrawal of the tar from the pressure still 1 and thereduction of pressure between the pressure still and the receiving tank24 may be regulated by means of a valve 25 in the line 18. The tarcollecting in the receiving tank 24 is withdrawn through the connection26 by meansof a pump 27. Vapors liberated in the receiving tankescapethrough connections 28, and can be discharged to the condenser 29through connection 30, or may be otherwise withdrawn through the outletconnection 32.

A cooling coil 33 is arrangedwithin the receiving tank, and may beregulated or cut out by means of valves 34 and 35.

The tar withdrawn from the receiving tank 24 is discharged into theagitator 36 where it is admixed with finely divided fullers earth or thelike. The treating agent is introduced into the agitator through chute37 from the elevated bin 38. A power driven mixer 39 is provided in theagitator for distributing the treating agent through the tar The admixedtar and treating agent are discharged from the agitator throughconnection 40.

From the agitator 36, the admixed tar and fullers earth, or othertreating agent, are introduced into one of a series of settling tanks41, 41, etc. through valved connections 42, 42', etc. A suflicientnumberof settling tanks can be provided to render the treatment of thetar-substantially continuous, and, it will be understood that the tarfrom one still or from battery of stills can be handled in a singletreating apparatus of appropriate capacity. In the settling tanks e. g.41, the treating agent and'the associated tarry constituents are allowedto settle and the oil from A which the tar has been more or lesscompletely A fpump 47 is provided for returning the clari ed oil fromthe storage tank through the line 21 to the pressure still for carryingout the cycl c process of the invention; or the clarified oil may bewithdrawn through the valved outlet 48 for introduction into otherpressure stills or for other suitable purposes.-

When the clarified oil is returned to the ressure still through the line.21, the valve 22 is closed and the valve 20 is opened. Any tain thecharge in the pressure still approxicondensate from the condenser 29 canbe discharged into the storage tank 44 through connection 49 andreturned to the pressure still through line 21 with the clarified oil,or withdrawn with the clarified oil through connection 48, or thiscondensate may be Withdrawn through connection 50 and put to other use.

In the operation of an apparatus such as that diagrammaticallyillustrated in the drawing, the pressure still will be charged, forexample, with a gas oil charging stock and the cracking operation willbe carried out in much the usual manner. During the early part of thecracking operation, the formation of tarry or carbonaceous constituentstakes place slowly and for a considerable period of time there is nooccasion for the withdrawal of the tar. When however, the amount oftarry constituents accumulating in the oil has reached the saturationpoint or has increased to such a degree as to make it desirable toprevent further accumulation of tarry constituents in the oil, thewithdrawal of tar begins and this withdrawal may take place continuouslyduring the remainder of the run.

The tar thus withdrawn is admixed with the fullers earth and the earthand tar are intimately admixed with each other so that the fullers earthcomes into contact with all parts of the tar. The earth-treated tar isthen permitted to settle so that the fullers earth will settle to thebottom of the settling tank and will drag down with it all or thegreater part of the tarry constituents. After the oil has beensufliciently settled, the oil may be withdrawn and returned to thepressure still. a

As an example of the practice of the process of the present invention inapparatus of the character illustrated, the pressure still may initiallybe charged with from 8,000 to 10,000 gallons of a gas oil charactercharging stock and brought to cracking conditions of temperature andpressure, distillate may then be taken off and fresh charging stockintroduced at a corresponding rate for a period while the amount oftarry constituents in the charge are building up, during this periodthe'rate of distillate oil may be from 800 to 1,000 gallons per hour andthe rate of fresh feed about 1,000 gallons per hour, before theaccumulation of tarry constituents tar may be withdrawn at a rate ofabout 1,500

- gallons per hour, and the rate of distillate 01f maintained at about1,000 gallons per hour, to maintain the concentration of tarryconstituents in the charge below an objectionable value. This tarwithdrawn may be treated for separating the tarry constituents from theassociated oil and the clarified oil returned to the pressure still andadditional charging stock may be introduced to mainmately constant.Before the conclusion of the run, the withdrawal of tar and the returnof the clarified oil and the additional charging stock may be terminatedand the concentration of tarry constituents in the charge allowed tobuild up during the final period of operation. W'here fresh chargingstock is introduced through the reflux tower on a pressure still inamount corresponding to the amount of distillate taken off, the returnedclarified oil and any additional fresh stock may be introduced directlyinto the still proper, for example, in a pressure still of the typeillustrated, the returned clarified oil may be introduced into thecirculating line and the additional charging stock through thecirculating pump.

It will thusbe seen that the present invention provides a new andimproved method of treating pressure still tar or similar tarry productsfrom cracking operations for the separation of the tarry constituentsfrom the oil with which they are admixed or in which they are dissolvedor carried in suspension; and that this fullers earth treatment canadvantageously be combined in a cyclic process in which the clarifiedand recovered oil is returned and subjected to further cracking in thepressure still from which the tar is withdrawn, or in other pressurestills where charging stock of the character thus recovered will undergofurther cracking. It will also be seen that the process of the inventionprovides an improved oil product which has several important advantagesfor use as pressure still charging stock or as a fuel oil or for otherpurposes where a clarified oil of low viscosity is required.

I claim 1. The method of treating oil mixtures containing tar producedby the cracking of hydrocarbon oils under pressure when heated toapproximately the cracking temperature, which comprises subjecting thetar and oil to a substantial reduction in temperature and dispersingthercthrough finely divided adsorbent material, and thereafterseparating the adsorbent material and accompanying tar from theremaining substantially tar free oil.

2. A method of treating oil mixtures containing tar produced by thecracking of hydrocarbon oils under pressure, which comprises vaporizingthe lighter oily constituents from the oil mixture, dispersing throughthe tar and remaining oil finely divided adsorbent material, andseparating the adsorbent material and accompanying tar from theremaining substantially tar free oil.

3. The improvement in the operation of pressure stills for crackinghydrocarbon oils which comprises withdrawing from the pressure still,during the cracking operation pressure still tar, vaporizing lighteroily constituents from the tar thus Withdrawn, subjecting the'unvaporized tar to treatment with finely divided adsorbent material,separating the adsorbent material and accompanying tarry constituentsfrom the treated oil, and 5 returning the treated oil to the pressurestill. 4. The improvement in the operation of pressure stills forcracking hydrocarbon oils which comprises withdrawing from the pressurestill, during the cracking operation pressure still tar, vaporizinglighter oily constituents from the tar thus withdrawn, subjecting theunvaporized tar to treatment with finely divided adsorbent material,separating the adsorbent material and accompanying tarry constituentsfrom the treated oil, collectingthe vaporized constituents and returningthem ,and the treated oil to the pressure still. 5. The improvement inthe operation of pressure stills for cracking hydrocarbon oils, whichcomprises withdrawing tar and adding fresh charging stock during theprogress-of the cracking operation to maintainthe pressure-still chargebelow saturation with tarry constituents, subjecting the tar thuswithdrawn to treatment with finelydivided adsorbent material, separatingthe adsorbent material and accompanying tarry constituents from the oil,and returning the treated oil to the pressure still.

The improvement in the operation of pressure stills for crackinghydrocarbon oils, which comprises withdrawing tar during the progress ofthe cracking operation, subjecting the tar thus withdrawn to treatmentwith finely divided adsorbent material, separating the adsorbentmaterial and accompanying tarry constituents from the oil, returning thetreated oil to the pressure still, and controlling the rate of tarwithdrawal from and supply of oil to the pressure still to to maintainthe pressure still charge below saturation with tarry constituents.

In testimony whereof I afix my signature. EDWARD W. ISOM:

